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1、电磁式继电器的结构、工作原理与特性Thestructure,principleandcharacteristicsofelectromagneticrelayTherelayisbasedonthechangeofsometypeofinputsignal,throughordisconnectingthecontrolcircuit,torealizeautomaticcontrolandprotectionofautomaticelectricalappliances・Manydifferentkindsofrelay,
2、accordingtothenatureoftheinputsignalisdividedinto:voltagerelay,currentrelay,timerelay,temperaturerelay,relayspeed,pressurerelays,etc・；Theprincipleofworkcanbedividedinto:electromagneticrelay,inductionrelay,electrodynamicrelay,thermalrelayandelectronicrelay,etc・Theou
3、tputcanbedividedintotwocategories:contactandnon-contact,whichcanbedividedinto:controlandprotectionrelay.ThestructureandworkingprincipleofelectromagneticrelayElectromagneticrelayistheearliestandmostwidelyusedtype.Itsstructureandworkingprincipleareroughlythesameasthe
4、contacts・Theelectromagneticrelayprincipleisshowninfigure1,whichconsistsofelectromagneticsystem,contactsystemandreleasespring.Sincetherelayisusedtocontrolthecircuit,thecurrentofthecontactissmall(undertheaverage5A),soitdoesnotrequireanarcextinguishingdevice・Commonele
5、ctromagneticrelaysincludevoltagerelays,intermediaterelaysandcurrentrelay.CharacteristicsofelectromagneticrelayThemainfeaturesoftherelayaretheinput-outputcharacteristics,whicharecalledrelays・WhentheinputquantityoftherelayXincreasesfromzerotoX2,theoutputoftherelayisz
6、ero.WhentheinputXincreasestoX2,therelayabsorbsandoutputsaY1:IfXgoesup,Ystaysthesame・WhenXisreducedtoXI,therelaysarereleased,theoutputisreducedfromY1tozero,andifXcontinuestodecrease,theYvalueiszero.TheKf二XI/X2iscalledthereturncoefficientoftherelay,whichisoneoftheimp
7、ortantparametersoftherelay.Kfisadjustable・Suchasgeneralrelayrequireslessreturncoefficient,Kfvalueshouldbebetween0.1〜0・4,sowhentherelayisclosedafterabsorption,inputamountvolatiledoesnotcausefalseaction;Theunder-voltagerelayrequiresahighreturncoefficientandtheKfvalue
8、isabove0.6.SetuparelayKf二0.66,thesuctionvoltageis90percentoftheratedvoltage,andthevoltageislessthan50%oftheratedvoltage,andtherelayisreleasedandt
